As the field of computer science has matured, a variety of devices have been developed to allow users to input information into computer devices. One group of these devices is referred to as pointing devices. As the user moves the device or a component of the device, the pointing device generates position data corresponding to the movement of the pointing device. This position data is in turn translated into movement of a pointer image rendered on a display. Thus, by moving the pointing device, a user can associate the pointer image with data represented by other images rendered on the display. A user can then manipulate that data by activating a command action associated with the pointer, such as depressing a command button.
One particular category of pointing device allows a user to input information into a computer by moving a pen or stylus relative to a surface. For example, some computers now include a digitizing tablet that detects the position of a stylus relative to the tablet. As the stylus moves across (or, in some cases, above) the surface of the tablet, the tablet produces position data based upon the position of the stylus. With these computers, the digitizing tablet may be separate from the display, or it may be incorporated into the display. One example of this type of input device is employed by the Microsoft TabletPC.
The stylus pointing device conveniently allows a user to input data using the natural input technique of handwriting. For example, the Microsoft TabletPC can convert position data generated by writing on a tablet surface with the stylus into electronic ink, much like an actual pen writes ink onto paper. In an effort to increase the capability of the stylus pointing device, some computers are even capable of recognizing “gestures” made with a stylus. More particularly, these computers recognize specific movements made with the stylus as commands, such as commands to perform an action or to produce a character. For example, this type of computer may recognize an oversized “S” movement made with the stylus as a command to save an open file, or recognize a “<” or “>” movement made with a stylus as a command to shift the images rendered on the display left or right, respectively. Alternately or additionally, this type of computer may recognize the movement of the stylus in a “v” shape or in an “c” shape as a command to produce the text character “v” or “c”, respectively.
While the use of gestures significantly enhances the capabilities of a stylus pointing device, it is sometimes difficult for a user to know when a particular gesture has been properly recognized. Because the movement of the stylus will be different each time a gesture is made by a user, a particular gesture cannot always be accurately recognized. Accordingly, a user must typically make a complete gesture, and then wait to see if the gesture was accurately recognized. If the computer does not recognize a gesture, it will not take the desired action. Even worse, if the computer incorrectly recognizes the movement of the stylus as another gesture, it will subsequently perform an undesired operation which the user must then undo. Alternately, a user may inadvertently move the stylus and make a gesture that was not intended. With conventional computers, a user would not realize that he or she had accidentally made a gesture until the corresponding operation was executed. If the user does not realize that the computer accepts gestures made with a stylus, the user may not even understand why the operation was executed.